This invention is directed at antenna systems useful for capturing TV signals transmitted from satellites or transmitting microwave signals to satellites and is more particularly directed to a new and improved dual mode horn used in conjunction with a parabolic reflector (dish) to receive signals focused at the horn aperture by the reflector or transmit signals towards the reflector.
Satellite TV systems have become more prevalent as additional satellites have been placed in orbit. Reflector horns and receivers pull in signals broadcast by satellites at more than 22,000 miles away. It has been reported that about one million home antennas are now aimed at a band of satellites in geostationary orbit above the equator.
These are primarily C-band satellites, that is they transmit in the 3.7 to 4.2 gigahertz (GH.sub.z) waveband. There are also some satellites operating in the KU BAND i.e., at a frequency of 11.7 to 12.7 GH.sub.z. These satellites serve as low-power microwave repeater station.
The antenna systems used today are referred to as TVRO (TV-Receive Only) antennas and comprise a dish (reflector), a horn for receiving the reflected energy focused by the antenna towards the horn aperture and a low noise converter coupled to one end of the horn. Signals from the antenna are suitably amplified and feed to the users TV receiver.
A more recent improvement in such systems is the use of a new and improved offset parabolic antenna system which has significant advantages. Such offset parabolic systems substantically eleminates snow loading as well as substantically eleminating shadows cast by axisymmetrical parabolic designs and thus the adverse effect of the reflector on the horn is substantially reduced. In order to fully gain the benefits of an offset parabolic dish antenna, it became apparent that conventional horns would not be satisfactory and therefore a new and improved horn was needed. This invention provides such a unique dual mode conical horn to permit the benefits of an offset parabolic antenna system using e.g., the parabolic antenna dish (reflector) sold by Northern Satellite Corporation of 103 South Street, Hopkinton, Mass. 01748, to be realized. It should be understood that the horn of this invention can operate equally well to receive or transmit in conjunction with a parabolic dish (reflector) and is particularly advantageous when used in conjunction with a small focal length reflector because it can be made quite small in physical size comparison with the conventional single mode horn which could be used.
The horns of this invention may conveniently be constructed of a die cast zinc alloy or other metal materials.